Method of forming a headed thermoplastic tube

ABSTRACT

A headed thermoplastic tube is formed solely from a thermoplastic extruded, stretched, cylinder by positioning the cylinder over a forming mandrel with an exposed portion. The inner surface of the exposed portion is heated above the glass transition temperature of the thermoplastic material to render the inner surface molten while the outer surface provides support for the exposed portion of the cylinder. The heated exposed portion is then shaped into a conical shape, such as by heating the outer surface, and pressure applied to the conical shaped exposed portion to form a headed thermoplastic tube. The headed tubes produced have a body portion, shoulder portion and neck portion, without any seams, all of which are formed from the starting thermoplastic extruded, stretched cylinder.

FIELD OF THE INVENTION

The present invention relates to a method of forming headedthermoplastic tubes solely from an extruded thermoplastic sleeve withoutuse of any additional thermoplastic material

BACKGROUND OF THE INVENTION

Thermoplastic tubes that are formed as squeeze tubes are extensivelyused in packaging of cosmetics, toothpaste, shampoos, and the like.These tubes are formed as tubular members having an open end at a firstend and a threaded or other closure-acceptable head at the second end,with a closure used to seal the second end of the tube while thecontents of the tube are charged to the tube through the first end.After filling, the first end of the tube is closed, such as by heatsealing, to complete the filled tube for sale.

A problem has existed in formation of such tubes in that theclosure-acceptable head is usually formed separately from the tubularmember and provision of a complete seal between the head and tubularmember must be assured.

One well known commercial method for producing such headed tubes is thatdisclosed in U.S. Pat. No. 3,047,910 to M. H. Downs. In this process, atubular member is placed in a forming collar and a separate molten discof thermoplastic material forced into an open end of the tubular memberwhile retained by the forming collar. The latent heat of the molten discwelds the peripheral edge of the disc to the inner circumferential wallof the tubular member, and forms an end closure for the tubular member.Pressure is applied to the hot sealed end closure to shape the head intothe desired shape and an orifice then formed through the end of theclosure. The head is then fitted with a threaded cap or other closure toprovide a closed end tube ready for filling with the desired contentsfor the tube.

In methods such as that disclosed by the Downs, patent, somedifficulties remain, such as controlling of the thickness and weight ofthe head and exact color matching of the tubular member and the head.The Downs, process also can not be used to commercially prepare tubesfrom polycarbonates and polyvinyl chloride material. Also, any time twoseparate units such as a tubular member and head are combined, apossible source of weakness exists at the juncture of the two. Inaddition, with such a juncture, a joint between the tubular member andhead, a problem of providing a continuous barrier container is presentwhere the tube is formed of a barrier material, such as from anoxygen-barrier containing composite thermoplastic material.

There have been attempts in the past to produce thermoplastic squeezetubes by extruding a thermoplastic tubing, cutting the tubing intosleeves or tubular members, heating one end of the sleeve to a moltenmass and forming it into a head to make the thermoplastic tube. Thesemethods have not been successful because heat transfer is slow and themolten plastic difficult to control. In such attempts, a sufficientamount of molten thermoplastic cannot be accumulated on the end of thetube to form the desired head.

It is an object of the present invention to provide a method for forminga headed thermoplastic tube solely from a sleeve or tubular member.

It is another object of the present invention to provide a thermoplasticsqueeze tube having a head portion that does not have any joint orjuncture between the tubular portion of the tube and the head portionthereof.

SUMMARY OF THE INVENTION

A method of forming a headed thermoplastic tube from an thermoplasticextruded, stretched cylinder is provided by positioning the cylinderover a forming mandrel with an exposed portion of the cylinder extendingbeyond a head forming end of the mandrel. The inner wall surface of theexposed portion of the thermoplastic cylinder is heated to a temperatureabove the glass transition temperature of the thermoplastic material torender the inner surface area molten, such as by use of a blast of hotair directed against the inner wall surface, while maintaining the outersurface of the cylinder below the glass transition temperature so as toprovide support for the exposed portion of the cylinder and retain thecylindrical shape thereof The heated exposed portion is then shaped intoa conical shape, such as by directing hot air against the outer surfacethereof Pressure is then applied to the conical shaped exposed portionof the thermoplastic extruded cylinder to form a headed thermoplastictube. The pressure applied to the conical shaped exposed end portion ispreferably by forcing the same into an abutting die by use of the headforming end on the mandrel.

The extruded thermoplastic cylinder may be formed from a singlethermoplastic material or the cylinder may be formed from a laminate orcomposite of a plurality of layers of materials, one layer of which maybe an oxygen-impermeable material.

The tubes of the present invention are formed solely from athermoplastic extruded, stretched, cylinder and have a tube body,shoulder and neck, all of which are comprised of the thermoplasticmaterial from which the cylinder was formed, the tubes having no seamsor joints present throughout the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The present method will now be explained with reference to theaccompanying drawings wherein like numerals indicate like partsthroughout the drawings, and wherein:

FIG. 1 illustrates, in cross-section, a thermoplastic extruded,stretched, cylinder from which the method of the present invention formsa headed thermoplastic tube;

FIG. 2 illustrates the thermoplastic extruded, stretched, cylinder ofFIG. 1 supported on a forming mandrel having a head forming end;

FIG. 3 illustrates heating of the exposed inner wall surface of theexposed portion of the thermoplastic extruded, stretched, cylinder by ahot fluid;

FIG. 4 illustrates the shaping of the heated exposed portion of thethermoplastic extruded cylinder into a conical shape;

FIG. 5 illustrates pressure being applied to the conical shaped exposedportion of the thermoplastic extruded cylinder into an abutting die toform a head;

FIG. 6 illustrates a finished headed thermoplastic tube on the formingmandrel prior to release therefrom;

FIG. 7 illustrates the finished headed thermoplastic tube released fromthe forming mandrel;

FIG. 8 illustrates a finished headed thermoplastic tube formed by thepresent method from a multilayer thermoplastic extruded, stretched,cylinder having three layers; and

FIG. 9 illustrates a finished headed thermoplastic tube formed by thepresent method from a multilayer thermoplastic extruded, stretched,cylinder having five layers.

DETAILED DESCRIPTION

The headed thermoplastic tubes produced according to the present methodcan be formed from various thermoplastic materials. Such thermoplasticmaterials include, but are not limited to, high density polyethylene,low density polyethylene, polypropylene, a polyester such aspolyethylene terephthalate, polycarbonates, polyvinyl chloride, and thelike.

The headed thermoplastic tubes may also be formed from multi layers orlaminates of various plastic materials, such as a layer of anoxygen-impermeable material comprising a polyamide such as nylon, orethylene polyvinyl alcohol, a polyvinylidene chloride or the likesandwiched between two polyethylene outer layers. Also, five layercomposites, comprising outer layers of a thermoplastic such aspolyethylene, polypropylene, a polyester such as polyethyleneterephthalate, an inner layer of an oxygen-impermeable material, andadhesive layers between the oxygen-impermeable material and each outerlayer of thermoplastic to bond the same, can be used to formthermoplastic headed tubes according to the present method.

The thermoplastic headed tubes are formed from a flexible material andare readily squeezable and collapsible to force the contents of the tubeout of an orifice formed in the end of the tube at the head portion.They are generally of a size having a wall thickness of the cylindricalportion of between about 0.010 to 0.040 inch in thickness, while ashoulder of the neck portion of the tube will be thicker than the wallof the cylinder, generally between 0.035 to 0.045 inch thick. Since thetube is formed from an extruded cylinder, the wall thickness of thecylindrical portion will be very uniform, with a variance in wallthickness of the cylindrical portion being only about +or -10 percent.

The extruded cylinder from which the headed thermoplastic tube is formedis a cylinder cut from a tubular extrusion which has a wall thickness inthe molten state preferably two to three times the wall thickness of thefinal cooled extruded thickness. Such a tubular extrusion, as is known,is formed by extruding thermoplastic material from an extrusion annulusin a molten state and stretching the hot tubular form, in the directionof the longitudinal axis, into a tube or cylinder having a wallthickness one-half (1/2), one-third (1/3), or less, than the extrusionannulus. Such a stretch oriented extruded cylinder, when heated abovethe glass transition temperature of the thermoplastic material, due tothe plastic memory of the thermoplastic material, will increase inthickness to the thickness of the molten material exiting the extrusionannulus, and shrink in length, thus providing sufficient molten plasticmass to form a head on the cylinder according to the present method.When using high density polyethylene or low density polyethylene, forexample, the annulus would extrude a tubular form of about 1.5 inch indiameter having a wall thickness between about 0.040-0.046 inch, whichwould be stretched into a stretch oriented extruded cylinder of about1.0 inch in diameter having a wall thickness between about 0.015-0.018inch.

Referring now to the drawings, FIG. 1 shows a thermoplastic extruded,stretched extrusion from which a thermoplastic extruded, stretched,cylinder 3 is cut. The thermoplastic extruded, stretched, cylinder 3 isdisposed on a forming mandrel 5 that has a head forming end 7 formed ofa shoulder 9 and a reduced diameter portion 11, with an exposed portion13 of the thermoplastic extruded, stretched, cylinder 3 extending beyondthe head forming end 7 of the forming mandrel 5 (FIG. 2). Thethermoplastic extruded, stretched, cylinder 3 is frictionally held onthe forming mandrel 5, with only a small clearance, such as about a0.005 inch clearance, which maintains the cylinder in place, whilepreventing subsequent flow of hot fluid between the forming mandrel 5and the inner wall surface 15 of the thermoplastic extruded, stretched,cylinder 3.

With the thermoplastic extruded, stretched, cylinder 3 disposed on theforming mandrel, the inner wall surface 15 of the exposed portion 13 isheated by use of a heat source inserted into the open end of the exposedportion of the thermoplastic cylinder, such as by impingement thereon ofa hot fluid illustrated by the arrows in FIG. 3, such as air, from a hotair nozzle -7 which is sized so as to permit insertion thereof into theopen end 19 of the exposed portion 13. The hot air is directed outwardlytowards the inner wall surface and flows away from the head forming end7 of the unheated forming mandrel 5. The hot air nozzle 17 and formingmandrel 5 are reciprocally associated so that the hot air nozzle 17 canbe disposed in and removed from the exposed portion 13 of thethermoplastic extruded, stretched, cylinder. The hot air nozzle 7 isshown as reciprocally movable, indicated by the dashed arrow in FIG. 3,while alternately the same can be fixed and the forming mandrel can bereciprocally movable.

The hot fluid heats the inner wall surface 15 of the exposed portion 13to a temperature above the glass transition temperature of thethermoplastic material and melts the inner wall surface, while the outersurface 21 of the exposed portion 13 provides sufficient support tomaintain the exposed portion 13 as a substantially cylindrical shape.When sufficient heat has been applied to the inner wall surface 15 ofthe exposed portion 13 to melt the same, the hot air nozzle 17 isremoved from the exposed portion and the heated exposed portion 13 isshaped into a conical or fluted cone shape 25, such as by theapplication of additional heat of further hot fluid, indicated by arrowsin FIG. 4, such as hot air, from external hot air nozzles 23, whichheats the outer surface 21 of the exposed portion 13 of thethermoplastic extruded, stretched, cylinder 3 to a temperature above theglass transition temperature of the thermoplastic material and melts thesame and renders it in a moldable state. While heating of the outersurface 21 by a hot fluid may be used to form the conical shape, it isalso possible to continue the heating of the inner wall surface 15 ofthe exposed portion -3 until the outer surface no longer maintains thesubstantially cylindrical shape, such that a conical shape results inthe exposed portion. Because the thermoplastic extruded cylinder 3 is astretched material, when the exposed portion 13 is heated above theglass transition temperature, the plastic memory responds and theexposed portion -3 swells to a thickness of or substantially thethickness of the tubular extrusion thickness, generally about two tothree times the wall thickness of the thermoplastic extruded, stretched,cylinder. The hot exposed portion, when above the glass transitiontemperature in addition to swelling in wall thickness shrinks in thedirection of the axis of the cylinder and provides a mass of moldablethermoplastic material 27 for forming of a head.

After shaping of the heated exposed portion 13 of the thermoplasticextruded, stretched, cylinder 3 into the conical shape 25 of moldablethermoplastic material 27, pressure is applied through the head formingend 7 of the forming mandrel 5 to form a headed thermoplastic tube 29which comprises a body portion 30, shoulder portion 31 and neck portion33 having a closed end 35 to close the end of the cylinder 3. Theforming is carried out by applying pressure to the conical shapedportion 13, and, as illustrated schematically in FIG. 5, by theapplication of pressure by use of the head forming end 7 of the formingmandrel 5 and an abutting die 37. As illustrated, the die 37 may have ashoulder forming portion 39, neck forming section 41, and a closed endforming section 43 which are retained in separable mold sections 45 and47. While the forming mandrel 5 is illustrated as being reciprocable toform the conical shaped portion 13 on the forming mandrel 5 into theabutting die 37, the forming mandrel could be fixed and the abutting die37 reciprocated to cause application of pressure and formation of theheaded thermoplastic tube.

FIG. 6 illustrated the formed headed thermoplastic tube 29 after removalof the head from the mold 37, still retained on the forming mandrel 5,while FIG. 7 shows the stripping or unloading of the finished headedthermoplastic tube 29 from forming mandrel 5 for finishing or use. As isconventional, the closed end 35 of the thermoplastic headed tube issubsequently punctured to form an orifice 49 therethrough.

The thermoplastic headed tubes formed by the present method are tubeswhich have no seams or joints between the various portions. As shown inFIG. 7, the thermoplastic headed tube 29 has a body portion 30, shoulderportion 31 and neck portion 33, all of which are comprised of thethermoplastic material that the thermoplastic extruded, stretched,cylinder 3 was formed, and there are no seams or joints presentthroughout the entire tube The thermoplastic headed tube, ashereinbefore described, may be formed from a single thermoplasticmaterial or a laminate comprised of multilayers of thermoplasticmaterials, at least one of which may be an oxygen-impermeable material.FIG. 8, for example, illustrates a multilayer thermoplastic headed tube29a as would be produced according to the present method, having threelayers, an outer layer 51, intermediate layer 53 and inner layer 55,where the outer and inner layers 51 and 55 are formed of a differentthermoplastic material than the intermediate layer 53. For example, theouter and inner layers can comprise polyethylene while the intermediatelayer would be an oxygen-impermeable layer, such as a polyamide such asnylon, or ethylene polyvinyl alcohol, a polyvinylidene chloride, or thelike. FIG. 9 illustrates a multilayer thermoplastic headed tube 29b aswould be prepared using the present method, having five layers, an outerlayer 57, inner layer 59, intermediate impermeable layer 61, and twoadhesive layers 63 and 65, one of the layers of adhesive providedbetween the intermediate layer 61 and each of the outer and inner layers57 and 59. Such a tube could, for example, use polyethylene,polypropylene, or a polyester such as polyethylene terephthalate as theouter and inner layers, an oxygen-impermeable material such as nylon,ethylene polyvinyl alcohol, polyvinylidene chloride, as the intermediatelayer, and adhesive layers to bond the outer and inner layers to theintermediate layer.

EXAMPLE

As an example of the present method, an extrusion of a thermoplasticmaterial, a low density polyethylene, was made through an orifice sizeof 0.040 inch and stretched into a cylindrical form having a 3/4 inchinner diameter with a wall thickness of 0.015 inch. A thermoplasticextruded, stretched cylinder about 4 7/8 inches long was cut from thecylindrical form and was fitted over a forming mandrel with an exposedportion of about 7/8 inch extending beyond a head forming end of themandrel. The inner wall surface of the exposed portion was heated withhot air (about 1300° F.), above the glass transition temperature of thethermoplastic material while maintaining the outer surface thereof belowsaid temperature. The heated exposed portion was then shaped into aconical shape by heating the outer surface of the heated exposed portionwith hot air (1300° F.), and the conical shaped exposed portion pressedinto a abutting die to form a neck and shoulder on the cylindrical body.The resultant low density polyethylene tube had a body portion having a0.015 inch wall thickness and inner diameter of 1/4 inch, a neck portionof about 1/4 inch in length and 5/16 inch in diameter, with a wallthickness of about 0.040 inch, and a shoulder portion of about 1/8 inchin length, having a wall thickness of about 0.040 inch. The resultanttube thus had a total length of about 4 3/8 inches and had no seams orjoints between the body portion, shoulder portion and neck portion.

The present method thus provides for the formation of a headedthermoplastic tube from an extruded plastic sleeve without the need forwelding or fusing together of any separate components. The resultantheaded tube has no seams, welds or joints. With thermoplastic laminatescontaining a barrier layer, the absence of such seams or joints isespecially useful since there is a continuous barrier layer throughoutthe body portion, shoulder portion and neck portion. Complete control ofthe thickness and weight of the head portion of the tube can beachieved. Also, the color of the head portion and body portion will beexactly the same, and the decorative features of the body portion, suchas stripes or windows can be carried through and incorporated in thehead portion of the resultant tube.

What is claimed is:
 1. A method of forming a headed thermoplastic tube from an extruded cylinder of thermoplastic material have a continuous wall with inner and outer wall surfaces comprising:positioning a thermoplastic extruded, longitudinally stretched, cylinder over a forming mandrel having a head forming end, with an exposed portion of said thermoplastic cylinder, having an open end, extending beyond said head forming end; heating the inner wall surface of the exposed portion of the thermoplastic extruded, longitudinally stretched, cylinder, by use of a heat source inserted into the open end of said exposed portion of said thermoplastic cylinder, to a temperature above the glass transition temperature of said thermoplastic material, while maintaining the outer surface thereof below said temperature so as to provide support for said exposed portion, such that the heated exposed portion of said thermoplastic, extruded, longitudinally stretched cylinder is shaped into a conical shape by said heating which causes longitudinal shrinking and thickening of the wall of said heated exposed portion; and applying pressure to the conical shaped exposed portion of said thermoplastic cylinder to form a headed thermoplastic tube.
 2. The method of forming a headed thermoplastic tube as defined in claim 1, wherein said heating is effected by a hot fluid directed against the inner wall surface of the exposed portion of the thermoplastic extruded, stretched, cylinder.
 3. The method of forming a headed thermoplastic tube as defined in claim 2, wherein said hot fluid is directed against said inner wall surface and away from the head forming end of said forming mandrel.
 4. The method of forming a headed thermoplastic tube as defined in claim 2, wherein said hot fluid is air.
 5. The method of forming a headed thermoplastic tube as defined in claim 1, wherein further shaping of the heated exposed end to a conical shape is effected by heating of the outer surface of said heated exposed portion.
 6. The method of forming a headed thermoplastic tube as defined in claim 1, wherein pressure is applied to the conical shaped exposed portion of said thermoplastic extruded cylinder by forcing the same, by the head forming end of said forming mandrel, into an abutting die.
 7. The method of forming a headed thermoplastic tube as defined in claim 1, wherein said extruded cylinder of thermoplastic material comprises a laminate of a plurality of layers of material.
 8. The method of forming a headed thermoplastic tube as defined in claim 7, wherein at least one of said layers is comprised of an oxygen-impermeable material.
 9. A method of forming a headed thermoplastic tube from an extruded cylinder of thermoplastic material have a continuous wall with inner and outer wall surfaces, comprising:positioning a thermoplastic, extruded, longitudinally stretched, cylinder over a forming mandrel having a head forming end, with an exposed portion of said thermoplastic cylinder, having an open end, extending beyond said head forming end; directing a hot fluid against the inner wall surface of the exposed portion of the thermoplastic extruded, longitudinally stretched, cylinder and away from the head forming end of said forming mandrel, by use of a hot fluid nozzle inserted into the open end of said exposed portion of said thermoplastic cylinder, to heat said inner wall surface to a temperature above the glass transition temperature of said thermoplastic material, while maintaining the outer surface thereof below said temperature so as to provide support for said exposed portion, such that the heated exposed portion of said thermoplastic, extruded, longitudinally stretched cylinder is shaped into a conical shape by said heating which causes longitudinal shrinking and thickening of the wall of said heated exposed portion; and then further heating the outer surface of said heated exposed end to further shape said heated exposed portion of said thermoplastic extruded, longitudinally stretched, cylinder into a conical shape; and applying pressure to the conical shaped exposed portion if said thermoplastic cylinder to form a headed thermoplastic tube.
 10. The method of forming a headed thermoplastic tube as defined in claim 9 wherein hot air is directed against said outer surface of said heated exposed end to heat the same and wherein said fluid directed against said inner wall surface is hot air.
 11. The method of forming a headed thermoplastic tube as defined in claim 10, wherein pressure is applied to the conical shaped exposed portion of said thermoplastic extruded cylinder by forcing the same, by the head forming end of said forming mandrel, into an abutting die. 